1. Field of the Invention
An aspect of this disclosure relates to a projection optical system and an image projection device including the projection optical system.
2. Description of the Related Art
Recently, for a liquid-crystal projector that is widely known as an image projection device, a resolution improvement of a liquid-crystal panel, an improvement on brightness based on an efficiency improvement of a light-source lamp, and a price reduction are progressing. Further, small and light weight image projection devices that utilize DMD (Digital Micro-mirror Device) and the like become common, and the image projection devices are widely used not only in offices or schools, but also in households. Especially, as portability of front projectors are improved, front projectors are used for small conferences for several people. As a projection optical system to be mounted in such an image projection device, a projection optical system including a curved-surface mirror has been proposed (for example, cf. Patent Document 1 (Japanese Published Unexamined Application No. 2006-235516), Patent Document 2 (Japanese Registered Patent No. 4210314), and Patent Document 3 (Japanese Published Unexamined Application No. 2009-157223)).